Nov. 30 – 2B03 30/11/2011 10:26:00 AM
Friday – content not on the final exam.
What makes a particle “elementary”?
This goes back all the way to the Greeks. If a particle is truly
elementary, it cant be subdivided.
o No inner structure.
Standard model – fundamental particles are quarks and leptons.
Quarks - 6 flavours, only up and down are important though
(protons and neutrons).
o And Leptons – electrons and electron neutrinos – 1 colomn
only one important.
o With very energetic events, you can create the other ones –
normal life just 1 column though.
Baryonic – everything made up of protons and neutrons – NORMAL STUFF
WIMP dark matter would be “non-baryonic”
Not made up of protons and neutrons.
Baryons – 3 quarks. Mesons – 2 quarks.
4 force carriers – have to do w/ 4 forces.
Describing the 4 forces w/ force carriers.
o 60s, 70s – Feynman describing force in a new way.
o Photons are the force carriers of electromagnetic force.
o Weak force - has a couple different force carriers. Things
which have only been detected in high energy particle
o Strong force - force carrier is gluons (like elastic bands)
o Gravity – graviton (unobserved)
Grand unified theories of physics – combine 3 forces. Some possible, but no
theory has been tested and is confirmed. As we go earlier and earlier in the universe (1 second old) – forces
merged together. Today we have 4 forces; as we go back – we can
see when they unified (electroweak @ 12 seconds after).
THe more you go back, forces were 1.
A "theory of everything" would explain all 4 forces.
Matter vs. Anti matter
For every particle in the standard model, there is an anti particle.
o An opposite electric charge.
o eg. Up vs anti-up.
We can make anti-matter
Cosmic ray shower – high energy particle in space.
o can come from supernovae explosions, suns.
Proton from sun slamming into atmosphere (llike a makeshift
particle accelerator) – a bunch of reactions. Other particles form.
When an electron and positron hit each